When to remove a custom Click-Event from a UITableCellView

Question

in the past couple of days I have been optimizing my app and found some memory leaks. I have implemented a custom UIButton that has a public event that I subscribe to. On one UITableViewController the button is hosted in a UITableCellView and I am subscribing to this event:

Cell:

class SelectionButtonCell : UITableViewCell
{
    @IBOutlet weak var selectionButton: SelectionButton!
    @IBOutlet weak var label: UILabel!
}

UITableViewController:

override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell
{
    let selectionButtonCell = tableView.dequeueReusableCell(withIdentifier: "selectionButtonCell") as! SelectionButtonCell
    selectionButtonCell.selectionButton.clicked = // This leaks memory because nowhere in my code this is set to nil
    {
        // Some unimportant stuff.
    }

    return selectionButtonCell
}

Button:

public class SelectionButton : UIButton
{
    // MARK: - Events
    public var clicked: (() -> ())?

    public override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent?)
    {
        super.touchesEnded(touches, with: event)

        self.clicked?()
    }
}

How do I set this var back to nil? I did not find any function that will be called when navigating back (the UITableViewController is pushed onto a UINavigationController). Is it okay to simply iterate over all cells and set this back to nil in viewWillDisappear(_) or is there a nicer way?

I tried tableView:didEndDisplayingCell:forRowAtIndexPath but it seems that this is only being called when scrolling the UITableView.

Sure, I have edited the post and posted the definition of the event. I have stripped all other code for better readability. — inexcitus, Jan 16 '20 at 04:42
Thanks. Just need to know why you haven't gone for `UIButton.addTarget` which would be safer option as the `IBOutlet`'s get automatically dealloc once the `UIViewController` is dismissed or pop. — Sohil R. Memon, Jan 16 '20 at 04:44
How could I distinguish which cell was clicked then? The `sender` will give me the instance but not the index of the cell. Is it possible to use addTarget with a block or do I have to use a selector (probably the latter)? — inexcitus, Jan 16 '20 at 04:48
There are various ways to do such task. Check this out already answered question: https://stackoverflow.com/questions/20655060/get-button-click-inside-uitableviewcell — Sohil R. Memon, Jan 16 '20 at 04:52
Thank you, feel free to add your comments as an answer so I can accept them. — inexcitus, Jan 16 '20 at 04:54
Thanks but SO doesn't accepts only link neither the question which already has the answer :) So, let me know if you have any issues I will surely help. Happy Coding :D — Sohil R. Memon, Jan 16 '20 at 04:55

Jawad Ali · Accepted Answer · 2020-01-16T05:50:35.160

1

 override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell
    {
        let selectionButtonCell = tableView.dequeueReusableCell(withIdentifier: "selectionButtonCell") as! SelectionButtonCell
        selectionButtonCell.selectionButton.clicked = 
        { [weak self] in
            // Some unimportant stuff.
        }

        return selectionButtonCell
    }

Also there are number of ways Get button click inside UITableViewCell you are using closure

edited Jan 16 '20 at 05:50

answered Jan 16 '20 at 05:41

Jawad Ali

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Thanks, I used this solution because it works (deist is now called) and it is by far the easiest solution. – inexcitus Jan 16 '20 at 16:01

vadian · Answer 2 · 2020-02-17T17:44:35.773

You don't need the subclass of UIButton. And you don't need the IBOutlet

In SelectionButtonCell declare an IBAction and a callback. Connect the button to the action. In the callback pass the cell.

class SelectionButtonCell : UITableViewCell
{
    @IBOutlet weak var label: UILabel!

    var callback : ((UITableViewCell) -> Void)?

    @IBAction func buttonClicked(_ sender : UIButton)
    {
        callback?(self)
    }
}

In celForRow get the current indexPath from the cell

override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell
{
    let selectionButtonCell = tableView.dequeueReusableCell(withIdentifier: "selectionButtonCell") as! SelectionButtonCell
    selectionButtonCell.callback = { buttonCell in
        let actualIndexPath = tableView.indexPath(for: buttonCell)!
        ...
    }

    return selectionButtonCell
}

If cells in the tableview are not inserted, deleted or moved you don't even need the cell parameter in the callback closure. The captured indexPath parameter is still valid.

When to remove a custom Click-Event from a UITableCellView

2 Answers2